System and method for harvesting energy down-hole from an isothermal segment of a wellbore

ABSTRACT

Systems and methods of generating power in a wellbore extending through a subterranean formation are described. A swirling flow of pressurized fluid is passed through a vortex tube to generate a temperature differential between first and second outlets of the vortex tube. The temperature differential is applied to a thermoelectric generator configured to convert the temperature differential into a voltage. The thermoelectric generator produces electrical power that is transmittable to down-hole tools within the wellbore such as an inflow control valve.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to operations in a wellbore associatedwith the production of hydrocarbons. More specifically, the inventionrelates to a system and method of generating electrical power in thewellbore by controlling fluid flow within the wellbore, such as theinflow of a production fluid into the wellbore.

2. Description of the Related Art

Often instruments and tools that require electrical power are positionedat down-hole locations within hydrocarbon producing wells. For example,electrically powered sensors are employed to monitor temperature,pressure, flow rates and other down-hole conditions. Other electricallypowered tools deployed to down-hole locations are actively controlled toachieve various objectives. For instance, down-hole valves are oftenopened and closed for the long term management of reservoir performanceover a lifetime of the reservoir, which is often 20 years or more.Electrically conductive cables have been deployed to connect thesedown-hole tools to a power source disposed at a surface location. Thesecables are expensive and prone to failure in the harsh environment of awellbore.

There is a need in the industry for systems that can be installed atdown-hole locations within a wellbore to provide electrical power tosensors, valves or other wellbore instruments over time. Additionally,there is a need for systems that can manage the production of fluidsfrom wellbores which often extend through separate production zoneshaving distinct characteristics such as pressure, porosity and watercontent. If not properly managed, the variation in these characteristicscan contribute to undesirable production patterns.

SUMMARY OF THE INVENTION

Described herein are systems and methods for providing electrical powerin a down-hole environment. The systems and methods employ a vortextube, which is operable to generate a temperature differential inresponse to fluid flow therethrough. The vortex tube includes a firstrelatively warm outlet and a second relatively cool outlet, which areoperatively coupled to a thermoelectric generator. The vortex tube isoperable to generate the temperature differential in otherwise generallyisothermal segments of a wellbore.

According to one aspect of the invention, a power generation system forgenerating electric power in a wellbore formed in a subterraneanformation includes a source of pressurized fluid, a thermoelectricgenerator operable to generate a voltage in response to an appliedtemperature differential, and a vortex tube operatively coupled to thethermoelectric generator to apply the temperature differential thereto.The vortex tube includes an elongate hollow body, an inlet in fluidcommunication with the source of pressurized fluid, a first outlet inthermal communication with a radially outer region of the elongatehollow body, and a second outlet in thermal communication with aradially inner region of the elongate hollow body. The first outlet isoperatively associated with a high temperature input to thethermoelectric generator, and the second outlet is operativelyassociated with a low temperature input to the thermoelectric generator.

In some embodiments, the inlet of the vortex tube is operable to be influid communication with the subterranean formation, and the source ofpressurized fluid is a production fluid within a production zone of thesubterranean formation. In some embodiments, the first and secondoutlets of the vortex tube are operable to be in fluid communicationwith a production tubing such that a flow path defined between thesubterranean formation and the production tubing extends through thevortex tube.

In some embodiments, the power generation system further includes anelectrically powered down-hole tool in electrical communication with thethermoelectric generator, wherein the electrically powered down-holetool is operable to selectively receive power generated by thethermoelectric generator. In some embodiments, the electrically powereddown-hole tool is an inflow control valve configured for regulating aflow of fluids between an interior and an exterior of a productiontubing extending through the subterranean formation. In someembodiments, the power generation system further includes a powerstorage device electrically coupled between the thermoelectric generatorand the electrically powered down-hole tool.

In some embodiments, the vortex tube is configured as a counter-flowvortex tube with the first and second outlets disposed on longitudinallyopposite sides of the elongate hollow body.

According to another aspect of the invention, a power generation systemfor harvesting energy in a wellbore extending through a subterraneanformation includes a thermoelectric generator operable to generate avoltage in response to an applied temperature differential and a vortextube operatively coupled to the thermoelectric generator to apply thetemperature differential thereto. The vortex tube includes an elongatehollow body, an inlet operable to be in fluid communication with thesubterranean formation and operable to generate a swirling flow of aproduction fluid along a radially outer region of the elongate hollowbody, a first outlet disposed in the radially outer region of theelongate hollow body and operable to discharge a first portion of theswirling flow of production fluid, a restrictor operable to redirect asecond portion of the flow of production fluid from the radially outerregion of the elongate hollow body to a radially inner region of theelongate hollow body, and a second outlet disposed in the radially innerregion of the elongate hollow body and operable to discharge a secondportion of the swirling flow of production fluid. The first outlet isoperatively coupled to a high temperature input to the thermoelectricgenerator, and the second outlet is operatively coupled to a lowtemperature input of the thermoelectric generator.

In some embodiments, the vortex tube is disposed in an annular regiondefined between the subterranean formation and a production tubingextending through the subterranean formation. In some embodiments, theannular region is defined between two longitudinally spaced isolationmembers extending around the production tubing and engaging an annularwall of subterranean formation. In some embodiments, a pressuredifferential of about 300 psi is defined between an inlet to the vortextube and an aperture defined in the production tubing, wherein theaperture is in fluid communication with the first and second outlets ofthe vortex tube. In some embodiments, an inflow control valve isdisposed at an aperture defined in the production tubing, wherein theaperture is in fluid communication with the first and second outlets ofthe vortex tube, and wherein the inflow control valve is electricallycoupled to the thermoelectric generator to receive power therefrom.

In some embodiments, the power generation system further includes firstand second thermocouples respectively in thermal communication with thefirst and second outlets of the vortex tube, wherein the first andsecond outlets of the vortex tube are respectively operably coupled tothe high and low temperature inputs of the thermoelectric generatorthrough the first and second thermocouples. In some embodiments, therestrictor is movable with respect to elongate hollow body such that anannular orifice defining the first outlet of the vortex tube isadjustable in size. In some embodiments, the inlet of the vortex tube isin fluid communication with a perforation defined through a casingdisposed around the production tubing.

According to another aspect of the invention, a method of generatingpower in a wellbore extending through a subterranean formation includes(i) producing a production fluid from the subterranean formation intothe wellbore, (ii) passing the production fluid through a vortex tube togenerate a temperature differential between first and second outlets ofthe vortex tube, and (iii) converting the temperature differential intoa voltage.

In some embodiments, the method further includes transmitting electricalpower to a down-hole tool from a thermoelectric generator operativelycoupled to the vortex tube to convert the temperature differential intothe voltage. In some embodiments, the method further includes operatingthe down-hole tool to selectively pass the production fluid through anaperture defined in a production tubing extending through thesubterranean formation.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features, aspects andadvantages of the invention, as well as others that will becomeapparent, are attained and can be understood in detail, a moreparticular description of the invention briefly summarized above may behad by reference, to the embodiments thereof that are illustrated in thedrawings that form a part of this specification. It is to be noted,however, that the appended drawings illustrate only preferredembodiments of the invention and are, therefore, not to be consideredlimiting of the invention's scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a schematic cross-sectional view of a wellbore extendingthrough a plurality of production zones and having an electrical powergeneration system therein in accordance with an embodiment of thepresent invention.

FIG. 2 is an enlarged schematic cross-sectional view of the powergeneration, system of FIG. 1 illustrating a fluid flow path extendingthrough a vortex tube installed on the exterior of a production tubing.

FIG. 3 is a schematic cross-sectional view of a vortex tube for use inan alternate embodiment of the present invention.

FIG. 4 is a flow diagram illustrating an example embodiment of anoperational procedure in accordance with the present invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Shown in side sectional view in FIG. 1 is one example embodiment of awellbore 100 extending through three production zones 102 a, 102 b and102 c defined in a subterranean formation 104. The production zones 102a, 102 b and 102 c include oil or some other hydrocarbon containingfluid that is produced through wellbore 100. As will be appreciated byone skilled in the art, although wellbore 100 is described herein asbeing employed for the extraction of fluids from subterranean formation104, in other embodiments (not shown), wellbore 100 is equipped topermit the injection of fluids into subterranean formation 104, e.g., ina fracturing operation carried out in preparation for hydrocarbonextraction.

Wellbore 100 includes a substantially horizontal portion 106 thatintersects production zones 102 a, 102 b and 102 c, and a substantiallyvertical portion 108. In other embodiments (not shown), an orientationof wellbore 100 is entirely substantially vertical, or deviated to lessthan horizontal. In the example embodiment depicted in FIG. 1, lateralbranches 110 a, 110 b, and 110 c extend from substantially horizontalportion 106 into respective production zones 102 a, 102 b, 102 c, andfacilitate the recovery of hydrocarbon containing fluids therefrom. Inother embodiments (not shown) no lateral branches are provided.Substantially vertical portion 108 extends to a surface location 112that is accessible by operators for monitoring and controlling equipmentinstalled within wellbore 100. As depicted in FIG. 1, the surfacelocation 112 is a terrestrial location, and in other alternativeembodiments (not shown), the surface location 112 is a subsea location

Production tubing 122 extends from surface location 112 throughsubstantially horizontal portion 106 of wellbore 100. Production tubing122 includes apertures 124 defined therein, which permit the passage offluids between an interior and an exterior of the production tubing 122.Fluids entering through apertures 124 are transmitted through productiontubing 122 to surface location 112, where surface flow line 134 couplesproduction tubing 122 to a reservoir 136 for collecting fluids recoveredfrom the subterranean formation 104. A casing 142 is provided aroundproduction tubing 122, defining annular regions 144 a, 144 b and 144 ctherebetween. Perforations 146 or other openings are provided in casing142 to permit fluid flow into annular regions 144 a, 144 b and 144 cfrom respective production zones 102 a, 102 b, 102 c.

In this example embodiment, isolation members 132 are provided, whichare operable to fluidly isolate annular regions 144 a, 144 b and 144 cfrom one another. Isolation members 132 are constructed as swellablepackers extending around the exterior of the production tubing 122 andengaging an annular wall of subterranean formation 104. The isolationmembers 132 serve to isolate the production zones 102 a, 102 b and 102 cfrom one another within wellbore 100 such that fluids originating fromone of the production zones 102 a, 102 b and 102 c flow into respectivecorresponding annular regions 144 a, 144 b, 144 e.

Power generation system 150 is provided in wellbore 100 for generatingelectricity while controlling the inflow of production fluids intoproduction tubing 122 from annular region 144 a, 144 b, 144 c. Powergeneration system 150 generally includes vortex tube 152, thermoelectricgenerator 154, power storage device 156, and electrically powereddown-hole tools including flow sensors 160, 162, and inflow controlvalve 164 configured for regulating the flow of fluids betweenproduction tubing 122 and annular region 144 b. As described in greaterdetail below, flow of production fluids through vortex tube 152 isassociated with a temperature differential established within vortextube 152. This temperature differential is employed to drivethermoelectric generator 156, which in turn generates an electriccurrent. The electric current is delivered either directly to anelectrically powered down-hole tool such as flow sensor 162, or throughpower storage device 156, which supplies electrical power toelectrically powered down-hole tools such as flow sensor 160 and inflowcontrol valve 164. Inflow control valve 164 is configured as any type ofvalve with a gate, ball or other electrically powered closure memberoperable to selectively and adjustably permit or restrict fluid flowthrough aperture 124 defined in production tubing 122. As one skilled inthe art will recognize, power generation system 150 is also operable toprovide electrical power to other electrically powered down-hole tools(not shown), such as motors, solenoids, pumps, etc. and/or to surfaceequipment (not shown).

Vortex tube 152 also increases resistance in the flow of productionfluids from annular region 144 b into production tubing 122 with respectto the flow of production fluids from annular regions 144 a, 144 c intoproduction tubing 122. In some embodiments, this increase in theresistance to flow is employed to equalize or otherwise control therelative inflow of fluids from production zones 102 a, 102 b and 102 c.

Referring now to FIG. 2, power generation system 150 is described ingreater detail Vortex tube 152 includes an elongate hollow body 168 withan inlet 170 in fluid communication with perforation 146 in casing 142.Inlet 170 is arranged to generate a swirling flow of fluid enteringvortex tube 152 therethrough. Curved walls, helical protrusions or otherfeatures are contemplated for generating the swirling flow as known inthe art. A first outlet 172 is defined at a longitudinal end of elongatehollow body 168 opposite inlet 170, and a restrictor 174 is disposedwithin first outlet 172. In the embodiment depicted in FIG. 2,restrictor 174 is in the form of a cone valve movable longitudinallywith respect to elongate hollow body 168 such that an annular orifice176 disposed at a radially outer region 178 a of elongate hollow body168 is variable or adjustable in size. In other embodiments (not shown)restrictor 174 is stationary with respect to elongate hollow body 168such that annular orifice 176 is fixed. A second outlet 180 is definedat a longitudinal end of elongate hollow body 168 adjacent inlet 170.Second outlet 180 is disposed at a radially inner region 178 b ofelongate hollow body 168. Vortex tube 152 is configured as a“counter-flow” vortex tube with first and second outlets 172, 180disposed on longitudinally opposite sides of elongate hollow body 168.Other configurations are contemplated such as a “uni-flow” vortex tube(see FIG. 3) wherein first and second outlets are disposed on a commonlongitudinal side of an elongate hollow body.

A first thermocouple is 182 is coupled to elongate hollow body 168adjacent first outlet 172 and a second thermocouple 184 is coupled toelongate hollow body 168 adjacent second outlet 180. Thermocouples 182,184 are operably coupled to thermoelectric generator 154 such thatthermoelectric generator 154 converts a temperature differential definedbetween the thermocouples 182, 184 to a voltage. First thermocouple 182is operatively associated with high temperature input 154 a ofthermoelectric generator 154 and second thermocouple 154 b isoperatively associated with low temperature input 154 b ofthermoelectric generator 154. Thermoelectric generator 154 iselectrically coupled to power storage device 156, which in exemplaryembodiments is a rechargeable battery. Power storage device 156 isoperable to maintain the voltage generated by thermoelectric generator154 and selectively distribute power to inflow control valve 164 andflow sensor 160. In some embodiments (not shown) flow sensor 162 is alsocoupled to power storage device 156 rather than being directly coupledto thermoelectric generator 154.

Referring still to FIG. 2, a flow path is defined between productionzone 102 b in subterranean formation 104 and production tubing 122 thatextends through vortex tube 152. A production fluid produced underpressure from production zone 102 b enters inlet 170 of vortex tube 152through perforation 146 in casing 142 as indicated by arrow 188 a. Theinlet 170 is configured to generate a swirling flow of the productionfluid along radially outer region 178 a of elongate hollow body 168 asindicated by arrows 188 b. A first portion of the production fluid isdischarged through first outlet 172 as indicated by arrow 188 c.Restrictor 174 redirects a second portion of the production fluid fromradially outer region 178 a to radially inner region 178 b of elongatehollow body 168. A swirling flow of the second portion of the productionfluid traverses radially inner region 178 b and is discharged throughsecond outlet 180 as indicated by arrows 188 d. A radial temperatureseparation in the production fluid is observable with this type ofswirling, motion inside vortex tube 152. The production fluid exitingthrough first outlet 172 exhibits a higher temperature than theproduction fluid exiting through second outlet 180.

Once the production fluid has been discharged from vortex tube 152, theproduction fluid flows through annular region 144 b to inflow controlvalve 164 as indicated by arrows 188 e. The flow of production fluidthrough annular region 144 b is depicted as a generally uncontainedflow. In other embodiments (not shown), pipes or passageways areprovided to guide the flow of production fluid through annular region144 b.

The production fluid is selectively permitted to enter production tubing122 through inflow control valve 164 as indicated by arrows 188 f. Insome embodiments, a pressure differential of about 300 psi is definedbetween inlet 170 to vortex tube 152 and aperture 124 defined inproduction tubing 122. This pressure differential is at least in partdue to frictional forces imparted to the production fluid by vortex tube152. The friction al forces are partially dependent on a length anddiameter of vortex tube as well as a size and configuration of inlet 170and first and second outlets 172, 180. In some embodiments this pressuredifferential facilitates equalization or regulation of the flow ofproduction fluid into production tubing 122 from annular region 144 bwith respect to the flows of production from annular regions 144 a and144 c. In this manner, vortex tube 152 serves as a passive inflowcontrol device.

Referring now to FIG. 3, vortex tube 200 is depicted in accordance withan alternate embodiment of the present invention. Vortex tube 200includes elongate hollow body 202 with an inlet 204 arranged to generatea swirling flow of fluid entering vortex tube 200 therethrough. A firstoutlet 208 is defined at a longitudinal end of elongate hollow body 202opposite inlet 204. Restrictor 210 is disposed within first outlet 208,and a second outlet 212 is defined through restrictor 210. First outlet208 is disposed at a radially outer region 218 a of elongate hollow body202 and second outlet 212 is disposed at a radially inner region 218 bof elongate hollow body 202. Radial temperature separation in fluidflowing through vortex tube 200 causes first outlet 208 to exhibit ahigher temperature than second outlet 212. Thus, first and secondthermocouples 182, 184 are operable to be coupled to first and secondoutlets 208, 212, and to high and low temperature inputs 154 a, 154 b ofthermoelectric generator 154 to apply a temperature differential tothermoelectric generator 154.

The configuration of vortex tube 200 is described as a “uni-flow” vortextube with first and second outlets 208, 212 disposed on a commonlongitudinal side of elongate hollow body 202. The temperatureseparation observed in a uni-flow vortex tube is generally lessprominent than the temperature separation observed in a counter-flowvortex tube. A uni-flow vortex tube such as vortex tube 200 presentscertain advantages when placed in an annular space surroundingproduction tubing 122 (FIG. 2) where space is limited. For example, insome embodiments, first and second outlets 208, 212 disposed on a commonlongitudinal side of elongate hollow body 202 permit a larger diameterelongate hollow body 202 to be employed since there is no need for fluidto flow along an outside of vortex tube 200 in the manner describedabove with reference to arrows 188 e (FIG. 2).

Referring now to FIG. 4, an operational procedure 300 for use of powergeneration system 150 (see FIGS. 1 and 2) is described. A productionfluid is produced (step 302) from production zone 102 b such that theproduction fluid enters wellbore 100. The production fluid is thenpassed through vortex tube 152 to generate a temperature differentialbetween first and second outlets 172, 180 (step 304). The temperaturedifferential is converted to voltage (step 306) with thermoelectricgenerator 154 and first and second thermocouples 182, 184. Electricalpower is transmitted (step 308) from thermoelectric generator 154 to adown-hole tool such as inflow control valve 164. In some embodiments,the power is temporarily stored in power storage device 156 before beingtransmitted to inflow control valve 164. Inflow control valve 164 isoperated (step 310), employing the electrical power transmitted theretoto selectively pass the production fluid through aperture 124 defined inproduction tubing 122. In this manner, power generation system 150harvests energy stored in the production fluid by generating atemperature differential in a down-hole segment of wellbore 100, whichmay be generally isothermal, and employing the harvested energy to drivea down-hole tool.

The present invention described herein, therefore, is well adapted tocarry out the objects and attain the ends and advantages mentioned, aswell as others inherent therein. While a presently preferred embodimentof the invention has been given for purposes of disclosure, numerouschanges exist in the details of procedures for accomplishing the desiredresults. These and other similar modifications will readily suggestthemselves to those skilled in the art, and are intended to beencompassed within the spirit of the present invention disclosed hereinand the scope of the appended claims.

What is claimed is:
 1. A power generation system for generating electricpower in a wellbore formed in a subterranean formation, the powergeneration system comprising: a source of pressurized fluid, wherein thesource of pressurized fluid is a production zone in the subterraneanformation containing a hydrocarbon containing fluid, wherein thepressurized fluid is a production fluid produced under pressure theproduction zone; a thermoelectric generator operable to generate avoltage in response to an applied temperature differential; and a vortextube operatively coupled to the thermoelectric generator to apply thetemperature differential thereto, the vortex tube comprising: anelongate hollow body; an inlet in fluid communication with the source ofpressurized fluid, wherein the inlet of the vortex tube is operable tobe in fluid communication with the subterranean formation, wherein theinlet of the vortex tube is in fluid communication with the subterraneanformation through a perforation of a casing, the casing surrounding aproduction tubing; a first outlet in thermal communication with aradially outer region of the elongate hollow body, the first outletoperatively associated with a high temperature input to thethermoelectric generator; and a second outlet in thermal communicationwith a radially inner region of the elongate hollow body, the secondoutlet operatively associated with a low temperature input to thethermoelectric generator.
 2. The power generation system according toclaim 1, wherein the first and second outlets of the vortex tube areoperable to be in fluid communication with the production tubing suchthat a flow path defined between the subterranean formation and theproduction tubing extends through the vortex tube.
 3. The powergeneration system according to claim 1, further comprising anelectrically powered down-hole tool in electrical communication with thethermoelectric generator, wherein the electrically powered down-holetool is operable to selectively receive power generated by thethermoelectric generator.
 4. The power generation system according toclaim 3, wherein the electrically powered down-hole tool is an inflowcontrol valve configured for regulating a flow of fluids between aninterior and an exterior of the production tubing extending through thesubterranean formation.
 5. The power generation system according toclaim 3, further comprising a power storage device electrically coupledbetween the thermoelectric generator and the electrically powereddown-hole tool.
 6. The power generation system according to claim 1,wherein the vortex tube is configured as a counter-flow vortex tube withthe first and second outlets disposed on longitudinally opposite sidesof the elongate hollow body.
 7. A power generation system for harvestingenergy in a wellbore extending through a subterranean formation, thepower generation system comprising: a source of pressurized fluid,wherein the source of pressurized fluid is a production zone in thesubterranean formation containing a hydrocarbon containing fluid,wherein the pressurized fluid is a production fluid produced underpressure the production zone; a thermoelectric generator operable togenerate a voltage in response to an applied temperature differential;and a vortex tube operatively coupled to the thermoelectric generator toapply the temperature differential thereto, the vortex tube comprising:an elongate hollow body; an inlet operable to be in fluid communicationwith the subterranean formation through a perforation of a casing, thecasing surrounding a production tubing and operable to generate aswirling flow of the production fluid along a radially outer region ofthe elongate hollow body; a first outlet disposed in the radially outerregion of the elongate hollow body and operable to discharge a firstportion of the swirling flow of the production fluid, the first outletoperatively coupled to a high temperature input to the thermoelectricgenerator; a restrictor operable to redirect a second portion of theflow of production fluid from the radially outer region of the elongatehollow body to a radially inner region of the elongate hollow body; anda second outlet disposed in the radially inner region of the elongatehollow body and operable to discharge a second portion of the swirlingflow of the production fluid, the second outlet operatively coupled to alow temperature input of the thermoelectric generator.
 8. The powergeneration system according to claim 7, wherein the vortex tube isdisposed in an annular region defined between the subterranean formationand the production tubing extending through the subterranean formation.9. The power generation system according to claim 8, wherein the annularregion is defined between two longitudinally spaced isolation membersextending around the production tubing and engaging an annular wall ofsubterranean formation.
 10. The power generation system according toclaim 9, wherein a pressure differential of about 300 psi is definedbetween an inlet to the vortex tube and an aperture defined in theproduction tubing, wherein the aperture is in fluid communication withthe first and second outlets of the vortex tube.
 11. The powergeneration system according to claim 9, wherein an inflow control valveis disposed at an aperture defined in the production tubing, wherein theaperture is in fluid communication with the first and second outlets ofthe vortex tube, and wherein the inflow control valve is electricallycoupled to the thermoelectric generator to receive power therefrom. 12.The power generation system according to claim 7, further comprisingfirst and second thermocouples respectively in thermal communicationwith the first and second outlets of the vortex tube, wherein the firstand second outlets of the vortex tube are respectively operably coupledto the high and low temperature inputs of the thermoelectric generatorthrough the first and second thermocouples.
 13. The power generationsystem according to claim 7, wherein the restrictor is movable withrespect to elongate hollow body such that an annular orifice definingthe first outlet of the vortex tube is adjustable in size.